31 adults took part in a randomised, placebo-controlled, double-blind trial of intravenous acyclovir therapy (500 mg/m2 intravenously 3 times daily for 5 days) for acute herpes zoster. Acyclovir reduced pain, decreased erythema, prevented the formation of new lesions, and healed skin faster than did placebo. The duration of viral shedding was also significantly shorter in acyclovir recipients (2 days versus 5 days). However, 6 (35%) of 17 acyclovir recipients had recurrence of pain after the drug was discontinued, and acyclovir did not appear to affect post-herpetic neuralgia. Acyclovir therapy was associated with a transient rise in serum creatinine levels, and may have been related to nausea and vomiting. Intravenous acyclovir was effective therapy for acute herpes zoster but the ideal treatment regimen might be a lower daily dose given for a longer period.
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intravenous infusions of 5 mg/kg every 8 h for 5 days. This dose of acyclovir was about 40% of ours and was not associated with adverse reactions. When both studies are considered together, the daily dose we used seems to be higher than necessary for a therapeutic effect. Since the dose we used was associated with side-effects, a lower daily dose is probably indicated. However, recurrence of pain after cessation of acyclovir in our study is evidence that acute herpes zoster should be treated for longer than 5 days. Oral treatment is much more practical than intravenous treatment, especially for outpatients. Trials of oral acyclovir for acute herpes zoster are in progress. If these trials show that oral treatment is effective, we speculate that the ideal way to treat acute herpes zoster would be with 1-2 days of intravenous acyclovir (7’ 5 mg/kg every 8 h) followed by at least 10 days of oral drug. These are early days in antiviral chemotherapy. Now that acyclovir has been shown to produce clear-cut improvements clinically and virologically in acute herpes zoster, work must be done to optimise the dosage regimens. We thank the staff of the University Hospital emergency room, the diagnostic virology laboratory, Dr Charles D. Mitchell, Dr James Boen, Mr Ed Kirk, Dr Ron Keeney, and Mrs Marian Wallfred for their help. This study was supported by grants AM13083 and AM18883 from the National Institutes of Health and by a grant from the Burroughs Wellcome Company, U.S.A. Correspondence should be addressed to B. B., Box 198 Mayo, University of Minnesota Health Sciences Center, Minneapolis, Minnesota 55455 U.S.A.